Fig. 2. Vertical profiles of RMS turbulence intensity in the three flow treatments having a free-stream velocity of U=5 cm s^–1. Turbulence intensities were derived from ADV measurements of horizontal velocity at (A) the location of stimulus release and (B) the starting position of test animals, which was 1.5 m downstream from the stimulus source. Data for the smooth condition is the same as that shown in Fig. 1 and is included here for the sake of comparison. The bump and cylinder obstructions increased turbulence intensity near the sediment surface relative to unobstructed flow, an effect that persisted throughout the test section.